There are many devices available in the prior art for cleansing the interior of a tank or vat prior to refilling the vessel. As carrying vessels such as tank trailers and seagoing tankers have become larger, and labor costs has escalated, the desirability of automatic washing systems has increased. Such systems must scan all of the interior vessel surface with a high pressure cleansing solution which may be hot and/or corrosive. Furthermore, since the cleansing liquid is often recirculated with little or no filtration, the systems must be able to tolerate suspended particulate matter with clogging or breakdown.
Of the prior art devices, some include a plurality of nozzles which are rotated by a reciprocating piston arrangement driven by the pressure of the cleansing solution.
These piston operated devices may require complicated valving which can be clogged by suspended debris. Furthermore, the reciprocating piston requires too much energy, and may result in a significant pressure drop at the nozzles. Such pressure loss causes a marked decrease in the cleansing effectiveness of the devices.
Other prior art devices include a plurality of nozzles rotated by a turbine motor which is driven by the cleansing fluid. The turbine requires rather delicate needle or roller bearing mounting, and the bearings generally must be sealed to prevent exposure to the corrosing cleansing solution. Once the seals break down, a likely eventuality, the bearings cannot withstand the corrosion and the suspended particulate matter from the fluid, and soon fail.